US4117466A - Beat frequency interference rejection circuit - Google Patents

Beat frequency interference rejection circuit Download PDF

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Publication number
US4117466A
US4117466A US05/777,524 US77752477A US4117466A US 4117466 A US4117466 A US 4117466A US 77752477 A US77752477 A US 77752477A US 4117466 A US4117466 A US 4117466A
Authority
US
United States
Prior art keywords
frequency
signal
beat
transmitter
swept
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US05/777,524
Other languages
English (en)
Inventor
George Jay Lichtblau
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Checkpoint Systems Inc
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to US05/777,524 priority Critical patent/US4117466A/en
Priority to SE7704988A priority patent/SE427882B/xx
Priority to DK189477A priority patent/DK147169C/da
Priority to CA278,050A priority patent/CA1073076A/en
Priority to IT68071/77A priority patent/IT1082816B/it
Priority to GB20066/77A priority patent/GB1580412A/en
Priority to ZA00772858A priority patent/ZA772858B/xx
Priority to AU25352/77A priority patent/AU511099B2/en
Priority to JP5891677A priority patent/JPS53113492A/ja
Priority to FR7716143A priority patent/FR2384306A1/fr
Priority to ES459235A priority patent/ES459235A1/es
Priority to DE2725169A priority patent/DE2725169C2/de
Priority to MX170738A priority patent/MX143644A/es
Application granted granted Critical
Publication of US4117466A publication Critical patent/US4117466A/en
Priority to JP1983199111U priority patent/JPS5937910Y2/ja
Assigned to CHECKPOINT SYSTEMS, INC. reassignment CHECKPOINT SYSTEMS, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LICHTBLAU, GEORGE J.
Assigned to CHECKPOINT SYSTEMS, INC. reassignment CHECKPOINT SYSTEMS, INC. SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ARTHUR D. LITTLE, INC., LICHTBLAU, GEORGE J., LICHTBLEU, ANNE R.
Anticipated expiration legal-status Critical
Assigned to FIRST UNION NATIONAL BANK, AS ADMINISTRATIVE AGENT reassignment FIRST UNION NATIONAL BANK, AS ADMINISTRATIVE AGENT GUARANTEE AND COLLATERAL AGREEMENT Assignors: CHECKPOINT SYSTEMS, INC.
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2471—Antenna signal processing by receiver or emitter

Definitions

  • This invention relates to electronic security systems and more particularly to circuitry therefore to reject beat frequencies caused by an interfering transmitter signal.
  • the beat signal caused by interference of an interfering transmitter and the system transmitter contains frequency components which extend from substantially zero frequency up to at least two times the interfering signal frequency, while frequency components of the resonant tag will not extend as high due to the inherently limited Q of the tag circuit.
  • a high pass filter is provided which has a cut-off frequency sufficiently high to substantially block all frequency components produced by the resonant tag while passing frequency components caused by the beat process. This high pass filter is coupled to the security system detector to receive output signal therefrom and in response to an interfering beat to provide a signal for inhibiting the alarm for the duration of the beat interference.
  • FIGS. 2A and 2B are plots of the frequency spectrum of a beat frequency signal and a resonant tag signal respectively, useful in illustrating operation of the invention.
  • An electronic security system is shown in FIG. 1 and includes a transmitter 10 coupled to an antenna 12 operative to provide an electromagnetic field within a predetermined area to be controlled and which is repetitively swept over an intended frequency range.
  • a receiving antenna 14 at the controlled area receives energy electromagnetically coupled from antenna 12 and is coupled to an RF front-end 16 which includes an RF band pass filter and RF amplifier.
  • the output of the front-end 16 is applied to a detector 18, the output of which is coupled to a high pass filter 20 which is effective to pass only the higher frequency portion of the signal spectrum.
  • the output of filter 20 is applied to a low pass filter 22 which is effective to remove carrier frequency components and high frequency noise.
  • the output of filter 22 is applied to a signal processor 24 which includes noise rejection circuitry operative to discriminate intended signals from noise and to provide an output signal representative of the presence of a resonant tag circuit 15 in the controlled area. Such output signals are applied to an alarm 26 or other output utilization apparatus to denote detection of a resonant tag in the controlled area.
  • This system just described is the subject of the above-identified U.S. patents and is operative to detect tag presence in a controlled area and to provide an alarm indication thereof.
  • An interfering transmitter 28 and associated antenna 29 located in the vicinity of the security system produces a fixed frequency carrier within the swept frequency range of transmitter 10 and which can beat with the signal from transmitter 10 as it sweeps past the frequency of transmitter 28.
  • beat frequency signals caused by interfering transmitter 28 are discriminated against to prevent a false alarm in the presence of such interfering signals.
  • the output signals from detector 18 are applied to a high pass filter 30 which has a cut-off frequency sufficiently high to substantially block all frequency components produced by the resonant tag circuit 15, while passing frequency components caused by the beat interference between the signals from transmitter 10 and interfering transmitter 28.
  • the output signal from filter 30, which is representative of the beat note interference is coupled via a video amplifier 32 to a threshold detector 34.
  • the threshold detector includes a reference threshold defining a signal level below which no inhibiting signal is produced or needed by reason of the small interfering signal levels.
  • the threshold detector 34 Upon exceedance of the threshold level by the signals from video amplifier 32, the threshold detector 34 provides a signal to multivibrator 36 which provides an inhibit pulse of fixed duration, the duration corresponding to the duration of the beat frequency signal produced by beating of the fixed frequency signal of interfering transmitter 28 and the swept frequency signal from transmitter 10.
  • the inhibit pulse is provided to signal processor 24 for the purpose of preventing alarm actuation in the presence of such inhibit pulse.
  • the system is inhibited from producing a false alarm for the duration of the beat interference.
  • the processing of the inhibit pulse from multivibrator 36 to prevent energizing of alarm 26 can be accomplished by well known circuitry which typically would include a gate circuit operative in the presence of the inhibit pulse to prevent application of an energizing signal to alarm 26.
  • the inhibit signal derived from high pass filter 30 can be produced by different circuit means other than that illustrated.
  • the inhibit signal should be of fixed duration to minimize the effects caused by the bandwith of the inhibit signal channel.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Computer Security & Cryptography (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Burglar Alarm Systems (AREA)
  • Emergency Alarm Devices (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Noise Elimination (AREA)
US05/777,524 1977-03-14 1977-03-14 Beat frequency interference rejection circuit Expired - Lifetime US4117466A (en)

Priority Applications (14)

Application Number Priority Date Filing Date Title
US05/777,524 US4117466A (en) 1977-03-14 1977-03-14 Beat frequency interference rejection circuit
SE7704988A SE427882B (sv) 1977-03-14 1977-04-29 Interferensundertryckningskrets
DK189477A DK147169C (da) 1977-03-14 1977-04-29 Elektronisk sikkerhedssystem med interferensdetektering
CA278,050A CA1073076A (en) 1977-03-14 1977-05-10 Beat frequency interference rejection circuitry
IT68071/77A IT1082816B (it) 1977-03-14 1977-05-11 Circuito di reiezione delle interfere renze producenti frequenze di battimento
GB20066/77A GB1580412A (en) 1977-03-14 1977-05-12 Beat frequency interference rejection circuitry
ZA00772858A ZA772858B (en) 1977-03-14 1977-05-13 Beat frequency interference rejection circuitry
AU25352/77A AU511099B2 (en) 1977-03-14 1977-05-20 Beat frequency interference rejection circuitry
JP5891677A JPS53113492A (en) 1977-03-14 1977-05-23 Electronic protecting system and circuit for deleting interference of beat frequency
FR7716143A FR2384306A1 (fr) 1977-03-14 1977-05-26 Circuit d'elimination de frequences de battement pour dispositifs electroniques de securite
ES459235A ES459235A1 (es) 1977-03-14 1977-05-27 Sistema de seguridad electronico.
DE2725169A DE2725169C2 (de) 1977-03-14 1977-06-03 Elektronisches Sicherheitssystem
MX170738A MX143644A (es) 1977-03-14 1977-09-29 Mejoras a circuito para rechazo de interferencia en un sistema electronico
JP1983199111U JPS5937910Y2 (ja) 1977-03-14 1983-12-27 電子防備システムの干渉除去回路

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US05/777,524 US4117466A (en) 1977-03-14 1977-03-14 Beat frequency interference rejection circuit

Publications (1)

Publication Number Publication Date
US4117466A true US4117466A (en) 1978-09-26

Family

ID=25110489

Family Applications (1)

Application Number Title Priority Date Filing Date
US05/777,524 Expired - Lifetime US4117466A (en) 1977-03-14 1977-03-14 Beat frequency interference rejection circuit

Country Status (13)

Country Link
US (1) US4117466A (de)
JP (2) JPS53113492A (de)
AU (1) AU511099B2 (de)
CA (1) CA1073076A (de)
DE (1) DE2725169C2 (de)
DK (1) DK147169C (de)
ES (1) ES459235A1 (de)
FR (1) FR2384306A1 (de)
GB (1) GB1580412A (de)
IT (1) IT1082816B (de)
MX (1) MX143644A (de)
SE (1) SE427882B (de)
ZA (1) ZA772858B (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1983001331A1 (en) * 1981-10-08 1983-04-14 I D Engineering Inc Electronic security system with noise rejection
US4484182A (en) * 1981-07-01 1984-11-20 Shorrock Developments Limited Intruder detection apparatus for functioning free of disturbance while in close proximity to high-power pulse-moldulated radars
WO1985003588A1 (en) * 1984-02-06 1985-08-15 Close Leo R Electronic surveillance system employing the doppler effect
US4565996A (en) * 1984-02-06 1986-01-21 Mrs. Lawrence Israel Range limited coherent frequency doppler surveillance system
WO1987004283A1 (en) * 1986-01-10 1987-07-16 Checkpoint Systems, Inc. Security tag deactivation system
US4686517A (en) * 1982-07-21 1987-08-11 N.V. Nederlandsche Apparatenfabriek Nedap Field disturbance detection system
US4779077A (en) * 1987-04-13 1988-10-18 Lichtblau G J Continuously armed high reliability pulse train processor
US5508684A (en) * 1995-03-02 1996-04-16 Becker; Richard S. Article tag
EP0862065A2 (de) * 1997-02-04 1998-09-02 Plessey Semiconductors Limited Alarmsensor und Antennenanordnung
US20130201006A1 (en) * 2011-09-23 2013-08-08 Andrew Llc Detecting Passive RF Components Using Radio Frequency Identification Tags

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8600738A (nl) * 1986-03-24 1987-10-16 Nedap Nv Onderdrukking van valse alarmen als gevolg van aanraken.

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3818472A (en) * 1972-05-26 1974-06-18 K Mauk R.f. system for detecting unauthorized travel of articles through a selected zone
US3868669A (en) * 1973-04-13 1975-02-25 Knogo Corp Reduction of false alarms in electronic theft detection systems

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3696379A (en) * 1970-12-02 1972-10-03 Knogo Corp Apparatus for article theft detection
US3863244A (en) * 1972-06-14 1975-01-28 Lichtblau G J Electronic security system having improved noise discrimination
US3810147A (en) * 1971-12-30 1974-05-07 G Lichtblau Electronic security system
US3967161A (en) * 1972-06-14 1976-06-29 Lichtblau G J A multi-frequency resonant tag circuit for use with an electronic security system having improved noise discrimination
US3961322A (en) * 1974-07-02 1976-06-01 Lichtblau G J Real time signal discrimination circuitry

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3818472A (en) * 1972-05-26 1974-06-18 K Mauk R.f. system for detecting unauthorized travel of articles through a selected zone
US3868669A (en) * 1973-04-13 1975-02-25 Knogo Corp Reduction of false alarms in electronic theft detection systems

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4484182A (en) * 1981-07-01 1984-11-20 Shorrock Developments Limited Intruder detection apparatus for functioning free of disturbance while in close proximity to high-power pulse-moldulated radars
WO1983001331A1 (en) * 1981-10-08 1983-04-14 I D Engineering Inc Electronic security system with noise rejection
US4686517A (en) * 1982-07-21 1987-08-11 N.V. Nederlandsche Apparatenfabriek Nedap Field disturbance detection system
WO1985003588A1 (en) * 1984-02-06 1985-08-15 Close Leo R Electronic surveillance system employing the doppler effect
US4565996A (en) * 1984-02-06 1986-01-21 Mrs. Lawrence Israel Range limited coherent frequency doppler surveillance system
GB2164826A (en) * 1984-02-06 1986-03-26 Leo Richard Close Electronic surveillance system employing the doppler effect
US4595915A (en) * 1984-02-06 1986-06-17 Mrs. Lawrence Israel Electronic surveillance system employing the doppler effect
AU570891B2 (en) * 1984-02-06 1988-03-24 Marcia Israel Electronic surveillance system employing the doppler effect
US4728938A (en) * 1986-01-10 1988-03-01 Checkpoint Systems, Inc. Security tag deactivation system
WO1987004283A1 (en) * 1986-01-10 1987-07-16 Checkpoint Systems, Inc. Security tag deactivation system
US4779077A (en) * 1987-04-13 1988-10-18 Lichtblau G J Continuously armed high reliability pulse train processor
US5508684A (en) * 1995-03-02 1996-04-16 Becker; Richard S. Article tag
EP0862065A2 (de) * 1997-02-04 1998-09-02 Plessey Semiconductors Limited Alarmsensor und Antennenanordnung
EP0862065A3 (de) * 1997-02-04 1998-12-23 Mitel Semiconductor Limited Alarmsensor und Antennenanordnung
US5999090A (en) * 1997-02-04 1999-12-07 Mitel Semiconductor Limited Alarm sensor and antenna arrangement
US20130201006A1 (en) * 2011-09-23 2013-08-08 Andrew Llc Detecting Passive RF Components Using Radio Frequency Identification Tags
US9590761B2 (en) * 2011-09-23 2017-03-07 Commscope Technologies Llc Detective passive RF components using radio frequency identification tags
US10003431B2 (en) 2011-09-23 2018-06-19 Commscope Technologies Llc Detecting passive RF components using radio frequency identification tags
US10505663B2 (en) * 2011-09-23 2019-12-10 Commscope Technologies Llc Detecting passive RF components using radio frequency identification tags

Also Published As

Publication number Publication date
GB1580412A (en) 1980-12-03
JPS53113492A (en) 1978-10-03
DE2725169A1 (de) 1978-09-21
DE2725169C2 (de) 1985-08-22
JPS59118085U (ja) 1984-08-09
CA1073076A (en) 1980-03-04
IT1082816B (it) 1985-05-21
FR2384306B1 (de) 1983-05-13
AU511099B2 (en) 1980-07-31
AU2535277A (en) 1978-11-23
DK189477A (da) 1978-09-15
DK147169C (da) 1984-10-15
ZA772858B (en) 1978-04-26
JPS5937910Y2 (ja) 1984-10-20
ES459235A1 (es) 1978-08-01
SE7704988L (sv) 1978-09-15
MX143644A (es) 1981-06-17
FR2384306A1 (fr) 1978-10-13
DK147169B (da) 1984-04-30
SE427882B (sv) 1983-05-09

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Legal Events

Date Code Title Description
AS Assignment

Owner name: CHECKPOINT SYSTEMS, INC., NEW JERSEY

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LICHTBLAU, GEORGE J.;REEL/FRAME:007936/0635

Effective date: 19960502

AS Assignment

Owner name: CHECKPOINT SYSTEMS, INC., NEW JERSEY

Free format text: SECURITY INTEREST;ASSIGNORS:ARTHUR D. LITTLE, INC.;LICHTBLAU, GEORGE J.;LICHTBLEU, ANNE R.;REEL/FRAME:008000/0690

Effective date: 19960606

AS Assignment

Owner name: FIRST UNION NATIONAL BANK, AS ADMINISTRATIVE AGENT

Free format text: GUARANTEE AND COLLATERAL AGREEMENT;ASSIGNOR:CHECKPOINT SYSTEMS, INC.;REEL/FRAME:010668/0049

Effective date: 19991209